JERUSALEM, May 7 (Jeffrey Heller/Reuters) - Prime Minister Benjamin Netanyahu called on Monday for an early general election on September 4, a vote opinion polls say will renew his leadership mandate as Israel confronts Iran's nuclear ambitions.

My intention is to form as wide a coalition as possible in order to bring about stability and lead Israel in the face of the great challenges still ahead of us, Netanyahu told his cabinet in public remarks.

The next national vote was not due until October 2013, but new legislation that might force ultra-Orthodox Jews to serve in the military and an upcoming budget debate have threatened to unravel a governing coalition of religious and nationalist parties once seen as one of the most stable in Israel's history.

We are in a country that needs political stability. I would be very happy if we could complete our term and that was my goal, too, Netanyahu said.

Regretfully this instability has put a question mark on this and so I think the right thing to do is to go for a short election. We propose September 4, and afterward, God willing, the voters will give us a mandate.

On Sunday, Netanyahu said in a speech to a convention of his right-wing Likud party that he would seek an early vote in four months' time but did not disclose an exact date.

Israeli leaders have insisted the election campaign would have no impact on their decision-making with regard to Iran, which includes the possibility of launching an Israeli strike against its nuclear installations.

A Netanyahu victory two months before the U.S. election could give him leverage over Barack Obama on the Iranian and Palestinian issues while the president is still engaged in his own campaign and wary of alienating pro-Israel U.S. voters.

While the cabinet met, the governing coalition submitted a motion of dissolution to parliament. Once parliament votes to dissolve, the current administration will remain in office until a new elected government is sworn in.

LIKUD LEADS

Opinion polls show Likud will easily come out on top of the national ballot, giving a Netanyahu-led government a new four-year term to tackle what he has described as the most important challenge facing Israel - the prospect of a nuclear-armed Iran.

Political commentators have said Netanyahu is likely to end up with a similar coalition after the vote and had decided to preempt the ballot to capitalize on his strong poll showing. A system of proportional representation means there are 13 party groups in the present, 120-seat, single-chamber parliament.

Netanyahu and Obama have had a thorny relationship and the Israeli leader has come under pressure from Washington not to take unilateral military action against Iranian facilities suspected of being part of a project to produce atomic weapons.

Iran says its nuclear program is purely civilian. Israel is believed to be the Middle East's only nuclear-armed power.

On the subject of Iran, Netanyahu told his party convention he would not ease the pressure until the threat is truly removed.

Netanyahu has been urged by Washington and other world powers to allow beefed-up international sanctions on Iran to bite. He has voiced pessimism about the outcome of international nuclear talks with Iran due to resume in Baghdad on May 23.

While polls have shown strong support for Netanyahu's leadership, they have also indicated a wide majority of Israelis either oppose an Israeli strike on Iran or would favour an attack only if it were carried out with U.S. agreement. (Writing by Jeffrey Heller; Editing by Crispian Balmer and Alastair Macdonald)